Zinc　oxide　nanoparticles　(ZnO　NPs)　are　widely　used　as　food　additives,　especially　in　nutritional　foods.　However,　many　reports　have　demonstrated　their　toxicity　in　humans　and　other　biological　systems.　Our　study　has　confirmed　that　ZnO　NPs　can　induce　apoptosis　and　oxidative　damage　on　human　gastric　epithelium　cells　(GES-1).　Caseinophosphopeptides　(CPP)　are　also　used　as　functional　food　additives　that　sequester　prooxidant　metals　and　scavenge　free　radicals.　Herein,　we　investigate　the　combined　cytotoxicity　of　ZnO　NPs　and　CPP　for　the　first　time.　The　results　show　that　CPP　protects　GES-1　cells　from　oxidative　stress　induced　by　ZnO　NPs,　decreases　reactive　oxygen　species,　diminishes　the　level　of　malondialdehyde,　increases　the　content　of　glutathione　and　improves　the　activity　of　superoxide　dismutase.　Therefore,　CPP　can　protect　GES-1　cells　against　ZnO　NP　induced　injury　through　the　down-regulation　of　oxidative　stress.